Despite the intensive study of Cretaceous marine temperatures using a variety of techniques, an equator–to-pole temperature profile for the Cretaceous greenhouse world remains poorly constrained.

We aim to address this significant gap in knowledge by undertaking the first quantitative and systematic study of early Cretaceous marine temperatures obtained from fossil molluscs using the novel clumped–isotope palaeothermometer.

This work will build upon the pilot study of Price & Passey (2013) based on data from the Yatria River, Siberia.

In order to construct an equatorial-polar temperature profile, we have selected early Cretaceous sites spanning 15 – 78 ºN of palaeolatitude [Morocco – Siberia]. The early Cretaceous (and Valanginian- Hauterivian in particular) has been selected as suitable material of this age is available for each of the study sites and therefore results are directly comparable.

All locations intended for study already have robust biostratigraphic frameworks, to place our findings in an appropriate context, and contain a rich and diverse benthic invertebrate fauna.

The Yatria River, Siberia

From our preliminary analyses (Price & Passey, 2013) we infer sub-arctic Early Cretaceous
marine temperatures ranging from 10°C to 20°C. These warm sub-arctic temperatures are warmer than present mean summer water temperatures at 60–65°N and are therefore consistent with a warmer “greenhouse” world featuring a shallow (equable) latitudinal temperature gradient.

Our combined temperature and δ18Obelemnite data imply seawater δ18O values that have a remarkably modern character in that they are similar to modern high-latitude seawater but more positive than modeled Cretaceous seawater.